This project is concerned with the genetics of the complement system, with cellular sites of synthesis, and with alterations of complement in vivo in normal individuals and in disease states. Genetic structural polymorphism will be sought in complement proteins using specific antisera. Attempts will be made to elucidate the broad outlines of the structure of GBG (properdin Factor B), particularly with respect to the subunit composition of the parent molecule and its activation fragments GGG and GAG. Proteins involved in the alternate (properdin) pathway to complement activation will be investigated and attempts at isolation, characterization, and definition of their roles in the reaction sequence and complement function will be made.